Revised September 2022!
EASA's most comprehensive technical document is available FREE to EASA members. Download the complete manual or just the sections you're interested in.

This manual covers horizontal and vertical squirrel-cage induction motors in the 300 to 5,000 horsepower range, low- and medium-voltage. Most of the principles covered apply to other sizes as well. This manual focuses primarily on IEC motors and standards.

This book was developed to help electric motor technicians and engineers prevent repeated failures because the root cause of failure was never determined. By using a proven methodology combined with extensive lists of known causes of failures, one can identify the actual cause of failure without being an “industry expert.” In fact, when properly used, this material will polish one’s diagnostic skills that would qualify one as an industry expert.

EASA’s Stator Core Test Form provides a step-by-step procedure for calculating the number of turns and cable size required for a loop test.

The International Electrotechnical Commission (IEC) standard 60529, “Degrees of protection provided by enclosures (IP code),” addresses the degrees of protection for electrical machines (motors and generators). The “IP” acronym means “international protection” but is sometimes referred to as “ingress protection.” The IP code is commonly displayed on the nameplates of metric machines that are manufactured to IEC standards.

Occasionally an end user wants to take a motor designed for horizontal mounting and use it in a vertical position. In this article, we will address some of the key mechanical factors that should be considered when applying a horizontal ball bearing motor in a vertical mounting position.

De vez en cuando un usuario final quiere utilizar un motor diseñado para montaje horizontal en posición vertical. En este artículo, trataremos algunos factores mecánicos clave que deben ser considerados cuando se utiliza un motor horizontal con rodamientos de bolas en una aplicación en la que trabaja en montaje vertical. La Figura 1 ilustra un motor horizontal en posición vertical con el eje hacia abajo.

Los factores clave incluyen:

• Capacidad de carga axial del rodamiento que soporta el peso del rotor.
• Peso del rotor
• Peso de los elementos acoplados al eje de salida
• Empuje axial de los equipos de impulsión acoplados directamente
• Trayectorias de lubricación de los rodamientos
• Retención del lubricante de los rodamientos
• Orientación del eje: Hacia abajo o hacia arriba
• Protección contra ingreso
• Fijación axial del rodamiento de empuje

The nameplate of an electric motor reveals much valuable information about the capability and performance of the machine.

La placa de datos de un motor eléctrico revela mucha información valiosa acerca de la capacidad y desempeño de la máquina.

When a modern temperature controlled (i.e., controlled pyrolysis) burnout oven is not available, the process described here can be used to burn out aluminum frame motors.

El método aquí descrito se puede utilizar para procesar motores con carcasa de aluminio cuando no se tenga un horno moderno de quemado con temperatura controlada (es decir de pirolisis controlada). 

Proper alignment of direct-coupled machinery is an essential element in reliability of a new or repaired machine (motor, pump, gear case, etc.). One common impediment to achieving proper alignment and smooth operation is a “soft foot” condition. This article looks at detecting soft foot, correcting soft foot and general recommendations for shims.

Realizar una correcta alineación de las máquinas acopladas de forma directa es un elemento esencial para garantizar la confiabilidad de operación de una máquina nueva o reparada (motor, bomba, caja de engranajes, etc.). Uno de los impedimentos comunes para lograr una alineación adecuada y un correcto funcionamiento, es el denominado  "pie suave".

We know that excessive temperature and moisture are the largest contributors to bearing and winding failures. Understanding the source of the increased temperature will help us to correct the problem and improve the machine’s life expectancy.

This presentation examines features, benefits and drawbacks of both conventional and alternative methods of cleaning electric motors.

Service centers routinely check the shaft extension runout of motors and generators. When there are issues associated with them, or when applicable, the coplanarity of the mounting feet and the amount of end foat of horizontal sleeve bearing motors and generators are checked.

Fundamental to every good mechanical repair is the ability to disassemble, repair and reassemble the motor correctly without unnecessary damage to any of the motor parts. This sounds simple, and yet too many costly mistakes are made in this process of taking things apart. If every motor repaired was in “as new” condition, the task would be much simpler. This manual introduces much of the basics to electric motor disassembly and assembly.

Due to economies of scale, the use of cast iron is a popular choice in the manufacturing of NEMA and IEC frames. Cast iron is robust and easily machined. It is dimensionally stable and transfers heat well. However, foundry work is an energy-intense process, not well-suited to limited production runs. For larger electric motors, which are manufactured in smaller quantities, the frame is more often fabricated from steel. You may have heard various nicknames for this type of construction: "shoe-box," "skeleton frame," "bathtubs" or other terms. Those who work on these motors regularly know that the frame requires care in handling, especially those fitted with sleeve bearings.

In the power transmission industry, a fair amount of cast iron is used. Whether it's for motors, pumps, or gear reducers, many use cast iron for the bulk of their structure. This variety of usage results in service opportunities involving the repair of cast iron components.

This book ws developed in conjuction with EASA's two-day Fundamentals of DC Operation & Repair Tips seminar.

This book is not meant to replace the many good texts that cover the theory and design of DC machines, but to supplement them. Its purpose is twofold: to help the technician understand DC machine theory without complex formulae; and in a larger sense, to record in one place the repair procedures and tips usually learned the hard way during a long career of DC machine repair. It may take a decade or longer for a technician to become proficient and knowledgeable. We hope this book will cut many years from that timeline.